1. Field of the Invention
The present invention relates to a bank note processing machine having a function of discriminating the bank note types and the genuineness/falsehood of bank notes, and more particularly to a compact bank note processing machine in which a compact discrimination sensor for irradiating bank notes with light having a plurality of wavelengths in the form of slits is provided such that the entire region of bank notes transported therethrough can be scanned to discriminate the bank note types and genuineness/falsehood of the bank notes based on light transmitted or reflected by the bank notes.
2. Description of the Prior Art
Various bank note processing machines (bank note discriminators) having a discriminating function for discriminating the bank note types and genuineness/falsehood of bank notes have been proposed including, for example, that disclosed in Japanese Patent Application Laid-open No. 312480/1998.
In the bank note processing machine disclosed in the above-cited publication, as shown in FIG. 1, a red LED array 102a and an infrared LED (Light Emitting Diode) array 102b are disposed in parallel to form a light source on one side of a transport path of a bank note 100, and a linear image sensor as a light receiving section 101 is formed on the other side opposite thereto to sandwich the same path. The red LED array 102a and infrared LED array 102b have a length that is substantially equal to the width of the bank note 100 passing by them. The output of the light receiving section 101 is inputted to a bank note genuineness/falsehood discrimination process section 104 to discriminate the genuineness/falsehood of the bank note 100. The reason for the use of the light source having a plurality of wavelengths is that there is a difference between the wavelengths of beams of light transmitted by a genuine bank note and a counterfeit bank note that is a color copy and the genuineness/falsehood can be determined based on the a difference between ratios of transmittance.
In the above-described conventional bank note processing machine, since the plurality of LED arrays 102a and 102b are disposed in parallel to form a discrimination sensor, the dimension of the light source section of the discrimination sensor inevitably becomes great in the direction in which bank notes are transported. As a result, it is necessary to provide the bank note transport path with a great dimension, which has resulted in a problem in that effort to make the bank note processing machine more compact is hindered. It is considered desirable to discriminate bank notes using a light source having many wavelengths from the viewpoint of improvement of accuracy of discrimination of the bank notes. For example, let us assume that a discrimination sensor is configured by disposing an array of LEDs in four rows having different wavelengths in parallel in order to perform discrimination with a light source having four wavelengths. Then, the sensor occupies considerably large dimensions. The sensor size (length) is increased further when a sensor having a light source with five wavelengths is used.